1. Field of the Invention
The invention relates to a fan-out circuit, and in particular, to a fan-out circuit with a small impedance difference and a display panel having the above-mentioned fan-out circuit.
2. Description of Related Art
With advantages of high definition, small volume, light weight, low driving voltage, low power consumption, and a wide range of applications, a liquid crystal display (LCD) has replaced a cathode ray tube (CRT) display and has become the mainstream display apparatus in the next generation. A conventional LCD panel is constituted by a color filter substrate having a color filter layer, a thin film transistor (TFT) array substrate, and a liquid crystal (LC) layer sandwiched between the color filter substrate and the TFT array substrate.
FIG. 1A is a schematic view of a conventional LCD panel. Referring to FIG. 1A, a conventional LCD panel 100 is divided into an active area 102 and a peripheral circuit area 104. A plurality of pixels 110 are disposed in the active area 102 to form a pixel array (not shown), and peripheral circuits 120 are formed in the peripheral circuit area 104. Each pixel 110 includes a TFT 112 and a pixel electrode 114 connected to the TFT 112. Each pixel 110 is surrounded by two adjacent scan lines 116 and two adjacent data lines 118. Usually, the scan lines 116 and the data lines 118 extend from the active area 102 to the peripheral circuit area 104 and are electrically connected to driver ICs 130 through the peripheral circuits 120. Generally, the driving ICs 130 have a particular design specification, so that the peripheral circuits 120 extend toward the driving ICs 130 from the terminals connecting the scan lines 116 and the data lines 118, so as to constitute a fan-out circuit 140.
FIG. 1B illustrates an enlarged schematic view of a fan-out circuit in the LCD panel shown in FIG. 1A. Referring to FIG. 1A and FIG. 1B simultaneously, each fan-out circuit 140 has a plurality of conductive lines 142. A distance between two terminals of conductive lines 142a on edges in an X direction is different from a distance between two terminals of conductive lines 142b at a center in the X direction. That is, with the different relative positions between the driving ICs 130 and the corresponding scan lines 116 or between the driving ICs 130 and the corresponding data lines 118, each conductive line 142 has a different length. Thus, the conductive lines 142 have notable impedance differences.
In order to reduce the impedance differences between the conductive lines 142, a part of the conductive lines 142 are designed with detouring portions 144 in many conventional techniques. The detouring portions 144 increases the length of the conductive lines 142 to adjust the impedance of different scan lines 116 or different data lines 118. However, a pitch between adjacent conductive lines 142 is usually fixed. The detouring portions 144 can only be circuitously arranged within this pitch. Consequently, the design of the detouring portions 144 merely reduces the impedance differences between the conductive lines 142 slightly. In other words, the outermost conductive lines 142a and the center conductive lines 142b of the same fan-out circuit 140 still have notable impedance differences.